Fine particle applicator and related methods

ABSTRACT

Embodiments relate to a fine particle applicator including a loading vessel, a metering roller positioned adjacent the loading vessel, a first stippling roller in contact with the metering roller, a high speed roller, positioned adjacent the metering roller such that bristles of the metering roller and bristles of the high speed roller overlap sufficient to form an interference zone, a second stippling roller, in contact with the high speed roller, a stippling shoe positioned adjacent at least the metering roller and high speed roller and a housing. At least a portion of a surface of the stippling shoe closest to at least the metering roller and high speed roller includes substantially the same curvature as the roller nearest the surface.

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 61/375,550, filed Aug. 20, 2010,which is incorporated herein by reference in its entirety.

BACKGROUND

Powder feeders and metering devices are used to measure the amount ofpowder or other flowable material being processed or applied to a targetor substrate. The rate of flow can be affected by such variables ashumidity, particle size, particle shape, density, material cohesiveness,and chemical composition. These alone, or in combination at times,render many existing powder feeders useless or troublesome.

Metering and aerating of fine particles for application on a substrateor target has been developed for easily flowable materials. But,application of materials that do not flow easily cause problems intraditional devices. Such materials are difficult to measure and meterin an applicator. These materials may form large or hard agglomeratesnaturally or when exposed to normally benign environmental conditions,such as slight humidity. Examples of such materials may be sugars orsalts. Aeration of these materials can be difficult and tribo-chargingmay also occur during an application process causing the material tostick together (form agglomerates) or stick to components of theapplication device.

SUMMARY

Embodiments relate to a fine particle applicator including a loadingvessel, a metering roller positioned adjacent the loading vessel, afirst stippling roller in contact with the metering roller, a high speedroller, positioned adjacent the metering roller such that bristles ofthe metering roller and bristles of the high speed roller overlapsufficient to form an interference zone, a second stippling roller, incontact with the high speed roller, a stippling shoe positioned adjacentat least the metering roller and high speed roller and a housing. Atleast a portion of a surface of the stippling shoe closest to at leastthe metering roller and high speed roller includes substantially thesame curvature as the roller nearest the surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate non-limiting example embodiments ofthe invention.

FIG. 1 is a cross-sectional view of a fine particle applicator,according to some embodiments.

FIG. 2 is a prospective view of a fine particle applicator, according tosome embodiments.

FIG. 3 is a front cut-away prospective view of a fine particleapplicator, according to some embodiments.

FIG. 4 is a rear cut-away prospective view of a fine particleapplicator, according to some embodiments.

FIG. 5 is a block flow diagram of a method of applying fine particles,according to some embodiments.

FIG. 6 is a cross-sectional view of a fine particle applicator system,according to some embodiments.

DETAILED DESCRIPTION

Throughout the following description, specific details are set forth inorder to provide a more thorough understanding of the invention.However, the invention may be practiced without these particulars. Inother instances, well known elements have not been shown or described indetail in order to avoid unnecessarily obscuring the invention. Thedrawings show, by way of illustration, specific embodiments in which theinvention may be practiced. These embodiments may be combined, otherelements may be utilized or structural or logical changes may be madewithout departing from the scope of the invention. Accordingly, thespecification and drawings are to be regarded in an illustrative, ratherthan a restrictive, sense.

All publications, patents and patent documents referred to in thisdocument are incorporated by reference herein in their entirety, asthough individually incorporated by reference. In the event ofinconsistent usages between this document and those documents soincorporated by reference, the usage in the incorporated referencesshould be considered supplementary to that of this document; forirreconcilable inconsistencies, the usage in this document controls.

In this document, the terms “a” or “an” are used, as is common in patentdocuments, to include one or more than one, independent of any otherinstances or usages of “at least one” or “one or more”. In thisdocument, the term “or” is used to refer to a nonexclusive or, such that“A, B or C” includes “A only”, “B only”, “C only”, “A and B”, “B and C”,“A and C”, and “A, B and C”, unless otherwise indicated. The terms“above” and “below” are used to describe two different directions inrelation to the center of a composite and the terms “upper” and “lower”may be used to describe two different surfaces of a composite. In theappended aspects or claims, the terms “first”, “second” and “third”,etc. are used merely as labels, and are not intended to impose numericalrequirements on their objects.

Embodiments of the present invention describe a fine particleapplicator. The applicator is capable of metering and dispensing sticky,cohesive or non-flowable materials in a usable form, including a formedprojected cloud of material that can be used with an electrostaticdeposition process, such as that typical of co-owned U.S. Pat. Nos.5,279,863 and 5,695,826.

Agglomerates that frequently occur when powders are handled sometimesfall into a category where they can be quite cohesive either byinterlocking mechanical forces or hygroscopic tendencies that producebonding water molecules (enabling surface tension forces) in even lowhumidity environments. Embodiments of this invention are unlike either adeagglomerator device which uses momentary rapid acceleration andsometimes wall impact, or the high speed brushes, which use a momentaryimpact with a relatively high speed bristle to break up theagglomerates. Additionally, embodiments of the present invention requireonly a fraction of the energy utilized by traditional devices andprocess. For example, in one embodiment, the tangential speed of thehigh speed roller is about 60 ft/min compared to about 1500 ft/min in aconventional device, which is about 1225 times less energy, for example.Embodiments described herein use a soft rotating brush bristle forcedagainst a hard smooth rotating element with surface speed differentialsbetween the two. In so doing, a smearing and possibly stippling actionoccurs which breaks up the large agglomerate. Even though the powdermight have sticking tendencies to the rotating element, multiplesmearing opportunities insure its removal. In addition, the stipplingrollers and optional air jet clean particles from the rollers, enablingthe device to self clean.

Referring to FIG. 1, a cross-sectional view 100 of a fine particleapplicator is shown, according to some embodiments. A loading vessel 102may feed a material to a metering roll 106. An optional agitator 104 maybe positioned in the loading vessel 102. Particles of the material mayenter a deagglomeration zone 126 before contacting the metering roll106. The metering roll 106 is positioned adjacent a stippling shoe 108,such as an upper stippling shoe 124. The particles are carried by themetering roll 106 to a first stippling roll 110, which is in contactwith the metering roll 106.

The particles may then be dropped into an aeration zone 130 beforecontacting a high speed roller 128. An optional air jet 118 or manifoldmay be positioned near the metering roller 106 and high speed roller 128in order to facilitate the removal of any particles not dropped from thehigh speed roller 128 or ultimately as fine particles 122. The particlesmay build a static charge and be attracted to a grounded portion (suchas a hub) of the high speed roller 128. The optional air flow providedby the jet 118 can disrupt the static attraction. The high speed roller128 may contact the stippling shoe 108, such as a lower stippling shoe112. The particles may be carried to a second stippling roller 114,where they are ejected as fine particles 122, such as fine powder ornear smoke-like consistency. A housing 116 surrounds the rollers andsubstantially contains the particles within the applicator. The fineparticles 122 may then coat or contact a target substrate 120.Interference zones 132 include the regions where rollers may contact,interact or overlap, for example.

The loading vessel 102 may be a hopper, for example. The vessel 102 mayhave a low, uniform depth. Material particles utilized in the applicatormay be materials (i.e., powders) that are difficult to flow, such assalts, sugars, cinnamon, micro-salt, soy protein, cocoa, whey protein,powdered cheese, corn and potato starch, menthol flavor and anti-mioticmaterials. Embodiments of the present invention may process materialswith a Hausner ratio between about 1.1 and about 1.7. The Hausner ratiomay be defined as the aerated volume of powder divided by its tampedvolume. If the material easily forms lumps or balls, an optionalagitator 104 may be utilized. The agitator 104 may be an additionalroller positioned at the distal portion of the loading vessel 102, atthe entry to the metering brush that may be powered cooperatively oroppositely to the metering brush. Alternatively, a reciprocating knifeat the distal end of the vessel 102 which would cut the lumps or ballsinto smaller pieces may be utilized. Another embodiment may be a seriesof sharp needles placed on a wall of the loading vessel 102, which mayreduce the size of the lumps as they were rotated by the bristles. Theneedles may be vibrated to provide additional abrasive functionality.The agitator 104 may be a stirrer, bar or reciprocating lever thatlevels powder in vessel 102, which may rotate, turn or otherwise agitateand reduces the size of a portion of the material before contact withthe metering roller 106.

The particles may contact the metering roller 106 in a deagglomerationzone 126 that is formed by the angle of the stippling shoe 108 andmetering roller 106. Any particles too large to penetrate the meteringroller 106 are pinched or trapped between the outer surface of theroller 106 and stippling shoe 108 and abraded by the roller 106 in thedeagglomeration zone 126, until reduced in size sufficient to be furtherprocessed. The stippling shoe 108 may be a single piece or be made oftwo or more parts, such as an upper stippling shoe 124 and lowerstippling shoe 112. The stippling shoe 108 may be a portion of a formedwall of the housing 116, for example. The upper stippling shoe 124 maybe positioned adjacent the metering roller and at least a portion of asurface the shoe closest to the metering roller 106 includessubstantially the same curvature. Similarly, the lower shoe 112 may bepositioned adjacent the high speed roller 128 and at least a portion ofa surface the shoe closest to the high speed roller 128 includessubstantially the same curvature. As the material is carried from themetering roller 106 to the first stippling roller 110, it may bestippled, smeared or both against the upper stippling shoe 124.Stippling refers to the action of short poking or flicking strokes(often in regard to a brush or bristles). The surface of the shoe may beconductive or insulative, depending on the material being processed. Thestippling shoe 108 may be touching or very nearly touching the outersurface of both the metering roller 106 and high speed roller 128.

The metering roller 106 may be a brush, for example. The bristles of thebrush may be fine, such as about 0.004 inches to about 0.008 inches indiameter. The bristles may be about 0.006 inches in diameter, forexample. The bristles may be nylon bristles, for example. The color andstiffness of the bristles may be adjusted to provide the proper amountof particle penetration and release. The high speed roller 128 may be abrush as well. The bristles of the brush may be fine, such as about0.010 inches to about 0.020 inches in diameter. The bristles may beabout 0.016 inches in diameter, for example. The length of bristles maybe many times their individual diameters. The metering roller 106 andhigh speed roller 128 may contact one another in order to assist withrelease of the particles and cleaning of the bristles. The bristles oneach roller may interfere or contact each other at a depth or overlap ofabout 1/32 inches to about 3/16 inches, for example. Each roller may beelectrically grounded to reduce electrical interaction with thematerial.

An optional air jet 118 or manifold may be positioned near the meteringroller 106 and force air into at least one of the metering roller 106 orhigh speed roller 128 to assist in cleaning particles off the rollersafter contacting each other. The air jet 118 may be one or more nozzlesor a precision slit, for example.

The particles penetrate the roller 106 in the deagglomeration zone 126and are carried to the first stippling roll 110. The metering roller 106and first stippling roller 110 may be operated together orindependently, so long as they are rotated in an opposite direction inorder to drop the particles into an aeration zone 130. The first andsecond stippling rollers 110, 114 may be solid rods. The rollers may beindependently driven by motors (see 202 of view 200, FIG. 2). Views 300and 400 of FIGS. 3 and 4, respectively, show cut-away views of theapplicator, including the use of a bulkhead 302 to support all rollers.

Gravity or forced air may then lead the particles to contact the highspeed roller 128 at the interface of the roller and stippling shoe 112.The particles slightly penetrate the roller 128 and are carried to thesecond stippling roller 114 where they are ejected as fine particles122. A fine cloud, not atypical of smoke is produced from theapplicator. Aerodynamic or gravimetric forces may then be used todeposit the particles 122 on a target substrate 120. Aerodynamic forcesmay cooperate with electrostatic forces as well, for applicationpurposes. An exhaust system may be positioned near or adjacent thedeposition or electrostatic zone. One example of an exhaust system maybe a vacuum used to gently pull the fine particles in the direction ofthe target substrate. The vacuum may exert less force or pull thaneither gravity or the electrostatic attraction of the particles to thesubstrate, for example.

The geometry of the metering roller 106 and first stippling roller 110and the high speed roller 128 and second stippling roller 114 cooperate.Each stippling roller may be positioned between the 90 degree positionof the larger roller (i.e., metering or high speed) and the 150 degreeposition (where top dead center is zero degrees). The stippling rollersmay be at least about ⅛ the diameter of the metering or high speedrollers, and not more than about ⅓ of their diameters.

Ratios of surface speeds are important. The metering roller 106 may beabout 3 inches to about 12 inches in diameter and the first stipplingroller 110 may be about ⅝ inches to about 1 inch in diameter with about1/32 inches to about 3/16 inches radial interference or overlap.

The stippling surface speed should desirably not exceed the meteringroll surface speed.

Examples of Operating Speeds

Metering Stippling Rotational Speed Rotational Speed Surface SpeedDifferential ⅓ RPM 1 RPM x1.73 ½ 1.2 2.16 ¾ 1.3 3.01

Similar brush and stippling roll diameters are used on the high speedroller.

High Speed Brush Stippling Rotational Speed Rotational Speed SurfaceSpeed Differential 86 RPM 168 RPM x2.66

Referring to FIG. 5, a block flow diagram 500 of a method of applyingfine particles is shown, according to some embodiments. Particles of amaterial are contacted with a rotating metering roller 502 in adeagglomeration zone, sufficient to control at least one of size, flowrate, mass or volume of the particles. The particles may be contactedwith a first stippling roller 504, sufficient to drop the particles fromthe metering roller. The particles may be contacted with a high speedroller 506, then contacted with a second stippling roller 508,sufficient to eject fine particles of a smaller size than beforecontacting the metering roller. The fine particles may then be deposited510 on a target substrate.

Referring to FIG. 6, a cross-sectional view 600 of a fine particleapplicator system is shown, according to some embodiments. One or morefine particle applicators 602 may be utilized in an application ordeposition system. In one embodiment, the applicators 602 may be placedadjacent each other, with each applicator 602 associated with anelectrostatic zone 604 and exhaust system 608. The target substrate 606may be positioned below the applicators 602, for example.

For additional precision in fine particle deposition, two applicatorsmay be used in tandem, with each applying about ½ of the neededmaterial. This may be particularly useful when the substrate is conveyedat high speed, as the applied charged particles do not completelydissipate their charge between the successive electrostatic depositions.Thus, the resulting uniformity is benefited during the secondapplication by the repulsive forces of the particulate already on thesubstrate “steering” the newly incoming material to uncoated or lessercoated regions.

The Abstract is provided to comply with 37 C.F.R. §1.72(b), to allow thereader to quickly ascertain the nature of the technical disclosure. Itis submitted with the understanding that it will not be used tointerpret or limit the scope or meaning of the claims.

What is claimed is:
 1. A fine particle applicator, comprising: a loadingvessel; a metering roller, positioned adjacent the loading vessel; afirst stippling roller, in contact with the metering roller; a highspeed roller, positioned adjacent the metering roller such that bristlesof the metering roller and bristles of the high speed roller overlapsufficient to form an interference zone; a second stippling roller, incontact with the high speed roller; a stippling shoe, positionedadjacent at least the metering roller and high speed roller; and ahousing; wherein at least a portion of a surface of the stippling shoeclosest to at least the metering roller and high speed roller includessubstantially the same curvature as the roller nearest the surface. 2.The applicator of claim 1, further comprising an agitator, positioned atleast partially within the loading vessel.
 3. The applicator of claim 1,further comprising an air jet.
 4. The applicator of claim 1, wherein thefirst stippling roller turns in an opposite direction as the meteringroller.
 5. The applicator of claim 1, wherein the second stipplingroller turns in an opposite direction as the high speed roller.
 6. Theapplicator of claim 1, wherein the stippling shoe comprises an upperstippling shoe and a lower stippling shoe.
 7. The applicator of claim 1,wherein the metering roller comprises a brush.
 8. The applicator ofclaim 1, wherein the high speed roller comprises a brush.
 9. Theapplicator of claim 1, wherein the metering roller and high speed rollerrotate in opposite directions.
 10. The applicator of claim 1, whereinthe interference zone comprises an overlap of about 1/32 inches to about3/16 inches.
 11. A method of applying fine particles to a target,comprising: contacting particles of a material with a rotating meteringroller in a deagglomeration zone, sufficient to control at least one ofsize, flow rate, mass or volume of the particles; contacting theparticles with a first stippling roller, sufficient to drop theparticles from the metering roller; contacting the particles with a highspeed roller; contacting the particles with a second stippling roller,sufficient to eject fine particles of a smaller size than beforecontacting the metering roller; and depositing the fine particles on atarget substrate.
 12. The method of claim 11, wherein particles compriseone or more of salts, sugars, cinnamon, micro-salt, soy protein, cocoa,whey protein, powdered cheese, corn and potato starch, menthol flavorand anti-miotic materials.
 13. A fine particle applicator system,comprising: two or more fine particle applicators; one or moreelectrostatic zones; and one or more exhaust systems; wherein the fineparticle applicator includes: a loading vessel; a metering roller,positioned adjacent the loading vessel; a first stippling roller, incontact with the metering roller; a high speed roller, positionedadjacent the metering roller such that bristles of the metering rollerand bristles of the high speed roller overlap sufficient to form aninterference zone; a second stippling roller, in contact with the highspeed roller; a stippling shoe, positioned adjacent at least themetering roller and high speed roller; and a housing; wherein at least aportion of a surface of the stippling shoe closest to at least themetering roller and high speed roller includes substantially the samecurvature as the roller nearest the surface.
 14. The applicator of claim13, wherein the metering roller and high speed roller rotate in oppositedirections.
 15. The applicator of claim 13, wherein the interferencezone comprises an overlap of about 1/32 inches to about 3/16 inches.